Can a jet fly inverted for an extended amount of time?

Question

Say there is a Boeing 737, and it rolls over to expose the belly of the aircraft. Now say it stays there for, lets say, 1 minute. If the pilot can set the pitch and hold the nose upright, will the aircraft sustain lift? Maybe that won't be a problem, but since the engines are using hydraulic fluids could the fluids continue to supply the engines?
Note that I am not talking about a roll, which I am sure is possible.

(PS: I dont want to know if a fighter jet can fly upside down, I mean passenger jets :P )

Answer 1

I think fuel would be your biggest problem. All engines mounted below the wing (where fuel is stored) can gravity feed to keep fuel moving to the engine driven fuel pumps. Remaining upside down would not allow you to maintain 1 postive "G" on the aircraft and it's fluids, and after a short time the fuel manifold would drain. The electric fuel pumps are normally mounted in the lowest part of the tanks and being inverted would undoubtely expose them, rendering them useless. Yes, Tex Johnston rolled the "Dash 80" (707 prototype) in a classic 1 G barrell roll.

Answer 2

Interesting question. The best I can offer is my skill at flying remote control airplanes. There are remote control airplanes that handle like passanger jets due to their wing shape, location and center of gravity. All I can say that theoretically it's possible but realistically very hard. They naturally want to roll back on their bellies and it takes a great amount of thrust to keep the wings producing lift. The angle of attack is greater. I believe it's possible. As for the hydraulic fluid and fuel feeding the proper mechanisms, I doubt that will be an issue, I can only imagine that the system is designed to take negative G's.

Answer 3

The amount of time meaning "extended" is up for debate but as long as the fuel & hydraulic pumps work, it's possible. Boeing test pilot Tex Johnson rolled the 707 on a demo flight, so they do OK upside down for short periods for sure.

Answer 4

Here is an actual picture taken during Tex Johnson's roll. As one answerer already stated, he accomplished it by using centrifugal force to maintain 1 positive G. Jet airliners are not like military jets in that they require the force of gravity to feed fuel to the engines. The basic fact of the matter is that sustained inverted flight is not possible in a modern jet airliner.



http://www.707sim.com/images/texrole.jpg



Here's a video of the roll-



http://www.alexisparkinn.com/photogallery/Videos/707%20Roll.mpg

Answer 5

Actually the issue isn't so much about the aircraft as it is about the stamina of the pilot. Hanging inverted in a harness for any length of time becomes "exhausting" on the pilot. If the aircraft has the power, it will continue to fly as long as the pilot is conscious.